Yeah, there's no perfect solution. Bicycles also produce microplastics and particles from tire shedding and brake pads. It's much much less than a car, but it still happens.

There is also a particular swampy area in a park with a paved bike path, where every year, there's a few dozen frogs flattened on the path. It's not common to other places where I ride, mostly just there. I was wondering if the heat of the asphalt might lure the frogs to bask on the path, and to their doom. However I've also ridden in the night and frogs sometimes just jump in your wheels. Maybe there's also just a bigger concentration there.

I've also seen terrapins lay their eggs in gravel paths. And I've never seen one dead, yet. In their case, asphalt might help a bit because they can't lay in the middle of the path, only the sides.

Plus, my point of view is also guided by the climate in my region, because asphalt can be plowed easily, and it also allows a cycling network to be open year round instead of just 6 months a year here. We can't cycle in mud or a metre of snow. Other regions might not have such extremes and can get away with well maintained dirt or gravel paths.

And I've never really ridden on wood chips for a long distance, only on decorative chips with soft beds. I'd be curious to try in some experimental spots. I would hope it's easier to roll on than grass. This also reminds me about some trails where they have multiple short wooden bridges to let nature cross in other ways.